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SYED: Symposium Electron-driven processes: Atomic-scale insights from theory and experiment

SYED 1: Symposium Electron-driven processes

SYED 1.4: Hauptvortrag

Donnerstag, 19. März 2020, 11:15–11:45, HSZ 01

Quantum localization and delocalization of charge carriers in molecular organic crystals — •Jochen Blumberger — University College London, Gower Street, London, WC1E 6BT, UK

Charge carrier transport (CT) in organic semiconducting materials is at the heart of many exciting and revolutionising technologies. Yet, our fundamental understanding of CT in the active layers of these devices that could rationalise experimental observations and guide further advances in the field is still rather limited. Charge carriers in organic semiconductors (OSs) are often described by one of two extremes: by a travelling wave propagating through the material or by a particle hopping from one molecular fragment to the next. Here we show that neither of these simplified pictures applies. Solving the time-dependent electronic Schrodinger equation coupled to nuclear motion for eight different organic molecular crystals, we find that the excess charge carrier forms a polaron delocalized over 10-20 molecules in the most conductive crystals.[1] The polaron propagates through the material by diffusive jumps over several lattice spacings (nanometers) at a time during which it expands to about twice its size. Computed localization lengths and charge mobility are in excellent agreement with experimental estimates, where available, and exhibit strong positive correlation in agreement with the recently proposed transient localization theory.

[1] S. Giannini, A. Carof, M. Ellis, H. Yang, O. G. Ziogos, S. Ghosh, and J. Blumberger, Nature Comm., vol. 10, p. 3843, 2019.